> ## Documentation Index
> Fetch the complete documentation index at: https://docs.thrindex.com/llms.txt
> Use this file to discover all available pages before exploring further.

# E0207 — BackendExecution (harness)

> The backend under test returned an error on a specific conformance sample.

<Warning>E0207: backend execution error on sample N</Warning>

## What happened

During a conformance harness run, the backend under test returned an execution error for sample `sample_idx`. The harness stops collecting results for this sample and reports the error.

## Why

The backend failed at runtime for this specific input. This could be:

* A driver crash on a particular input pattern
* A resource exhaustion that manifests only for certain input sizes
* An unhandled edge case in the backend's execution path (e.g. an all-zero input)

## How to fix

1. Isolate the failing sample: run the backend directly on sample `sample_idx` from the fixture set to reproduce the error outside the harness.
2. Check the `detail` field in the error message — it contains the backend's original error.
3. Fix the backend to handle this input class, then re-run the conformance suite.

## Example

```
E0207: backend execution error on sample 34: loihi2 driver timeout after 5000ms
Why: the backend-under-test returned an error during the conformance run
Fix: check the backend driver and the artifact compatibility
Docs: https://docs.thrindex.com/errors/E0207
```